Thermoplastic elastomer composition and process for producing the same

Abstract

A thermoplastic elastomer composition of the invention, formed by dynamically crosslinking a polymer composition including a rubber and an olefinic resin and having an average particle size of rubber particles within a specific range, shows an excellent balance of mechanical properties such as flexibility and elastic recovery, and a moldability. Also an inclusion of a (meth)acrylate resin and a hydrogenated diene polymer provides a composition particularly excellent in scratch resistance. Also an inclusion of a maleimide compound provides a composition particularly excellent in injection fusibility. Also an inclusion of an undenatured organopolysiloxane of a specific viscosity and a denatured organopolysiloxane provides a composition particularly excellent in initial slidability and durable slidability.

1. A thermoplastic elastomer composition prepared by a process which comprises:
 dynamically heat treating, in the presence of a crosslinking agent, a polymer composition comprising 
 a rubber, 
 an olefinic resin mixture comprising at least one crystalline olefinic resin and at least one amorphous olefinic resin, 
 a softening agent, 
 a (meth)acrylate resin, and 
 a maleimide compound, 
 wherein for the sum of said rubber, said olefinic resin mixture and said softening agent taken as 100 parts by mass, 
 said maleimide compound is present at a level of 0.3 to 10 parts by mass and 
 said (meth)acrylate resin is present at a level of 1 to 30 parts by mass. 
 
     
     
       2. The thermoplastic elastomer composition according to  claim 1 , wherein said polymer composition further comprises a hydrogenated diene polymer, wherein said hydrogenated diene polymer is present at a level of 0.1 to 1 in a mass ratio to said (meth)acrylate resin. 
     
     
       3. The thermoplastic elastomer composition according to  claim 1 , wherein the at least one crystalline olefinic resin comprises an α-olefin as a principal constituent unit in an amount of 80 mol % or more, based on total crystalline olefinic resin. 
     
     
       4. The thermoplastic elastomer composition according to  claim 1 , wherein the at least one crystalline olefinic resin has a crystallinity of 50% or higher, as measured by X-ray diffraction. 
     
     
       5. The thermoplastic elastomer composition according to  claim 1 , wherein the at least one amorphous olefinic resin comprises an α-olefin as a principal constituent unit in an amount of 50 mol % or more, based on total amorphous olefinic resin.